Facile fabrication of covalent organic framework composite membranes via interfacial polymerization for enhanced separation and anti-fouling performance

Covalent organic frameworks (COFs) have the advantages of high porosity, uniform and adjustable pore size, as well as superior compatibility with polymer, which are favorable for the production of defect-free films with high flux and excellent separation performance. In this work, TAPB-PDA COF thin films were synthesized by interfacial polymerization of benzaldehyde (PDA) and 1,3,5-tris (4-aminophenyl) benzene (TAPB) on polyethersulfone (PES) substrates with the aid of a catalyst. Different thicknesses of the COF films could be achieved by varying the concentration of the monomers. The TAPB-PDA COF/PES composite membranes exhibited enhanced removal capacities for organic matters compared to the pristine PES membrane, e.g., with the rejections of calcon (molecular weight of 416 g mol-1) and humic acid at 92.3% and 98.0%, respectively. Moreover, after the fouling of model organic pollutants or the filtration of natural surface water, the recovery coefficient of water permeability by hydraulic cleaning was 22–35% higher for the TAPB-PDA COF/PES composite membrane than that of the PES membrane. The improved anti-fouling performance was mainly attributed to the increased membrane surface hydrophilicity benefiting from the hydrophilic nature of the TAPB-PDA COF materials.